Catalog Add On: BETA Low-Voltage Circuit Protection ...

Correction factor; ambient temperature k u
The influence of the ambient temperature on the permissible load of
the SITOR fuse links is taken into account using the correction factor
k u as shown in the following graph.
u
Correction factor
'
&
" " $ &
Ambient temperature +
Correction factor; conductor cross-section k q
The rated current of the SITOR fuse links applies to operation with
conductor cross-sections that correspond to the respective test
cross-section (see the table on page 5/54).
In the case of reduced conductor cross-sections, the correction
factor k q , must be used as shown in the following graph.
k q
Correction factor
1,00
0,95
0,90
0,85
0,80
0,75
0,70
0,65
100 80 60 50 40 30 20 15 10
% Connection cross-section
(as a % of the test cross-section)
a = Reduction of cross-section of one connection
b = Reduction of cross-section of both connections
b
a
1 $ ! $
I2_12639
© Siemens AG 2007
BETA Protecting
SITOR Semiconductor Fuses
Siemens ET B1 AO · 2008, Characteristic curves
Configuration
Correction factor; conduction angle k λ
The rated current of the SITOR fuse links is based on a sinusoidal
alternating current (45 Hz to 62 Hz). However, in converter operation,
the arm fuses are loaded with an intermittent current, whereby the
conduction angle is generally 180 °el or 120 °el. With this load current
wave form, the fuse link can still carry the full rated current. In the
case of smaller conduction angles, the current must be reduced in
accordance with the following graph.
Correction factor
'
&
%
$
#
! " # $ ' & "
Valve conducting period
Correction factor; forced-air cooling k l
In the case of increased air cooling, the current carrying capacity of
the fuse link increases with the air speed, air speeds > 5 m/s do not
effect any significant further increase of current carrying capacity.
Correction factor
"
!
"
Air velocity
! $
A
$
I
1 $ ! &
1 $ ! %
4/55
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17